def ccw(x1, y1, x2, y2, x3, y3): c = (x2 - x1) * (y3 - y1) - (y2 - y1) * (x3 - x1) return c > 0 def convex_hull(positions): convex = [] for p3 in positions: while len(convex) >= 2: p1, p2 = convex[-2], convex[-1] if ccw(*p1, *p2, *p3): break convex.pop() convex.append(p3) return len(convex) n = int(input()) positions = sorted([list(map(int, input().split())) for _ in range(n)], key=lambda x: (x[..